In magnetic resonance (MR) imaging systems, gradient coil assemblies are used to generate gradient magnetic fields. These gradient magnetic fields are generated in three axial directions, i.e. in the x, y, and z-direction of the gradient coil assemblies. Accordingly, gradient coil assemblies comprise an x-coil, a y-coil, and a z-coil. The z-coil and the respective z-direction correspond to the longitudinal direction of the gradient coil assemblies.
State of the art gradient coil assemblies comprise a set of inner coils and a set of outer coils with one coil for each direction, whereby the set of outer coils and the set of inner coils are provided in concentric cylinders, which are spaced apart. The set of outer coils generally provides a shielding of the set of inner coils to avoid the generation of eddy currents due to the changing magnetic fields of the gradient coil assembly. When referring to a coil, usually conductors are referred to, since they are responsible for conducting electrical current and generating the gradient fields. Other components, e.g. supporting structures or the like, are not explicitly mentioned.
Such state of the art gradient coils assemblies, as e.g. known from U.S. Pat. No. 5,426,845 A, comprise coils, which are generally made of copper to minimize the dissipation therein. Dissipation comprises losses due to electrical and magnetic properties of the copper. Also, copper is a material with excellent conductive properties in respect to electric current and heat. Drawbacks of using copper are that copper is an expensive and heavy material, so that the gradient coil assemblies as well as the MR imaging systems comprising such gradient coils assemblies are difficult to handle and to install, and involve high manufacturing costs.